The human eye functions to provide vision by transmitting light through a clear outer portion called the cornea, and focusing the image by way of a crystalline lens onto a retina. The quality of the focused image depends on many factors including the size and shape of the eye, and the transparency of the cornea and the lens. When age or disease causes the lens to become less transparent, vision deteriorates because of the diminished light which can be transmitted to the retina. This deficiency in the lens of the eye is medically known as a cataract. An accepted treatment for this condition is surgical removal of the lens and replacement of the lens function by an artificial intraocular lens (IOL).
In the United States, the majority of cataractous lenses are removed by a surgical technique called phacoemulsification. A typical surgical hand piece suitable for phacoemulsification procedures consists of an ultrasonically driven phacoemulsification hand piece and an attached hollow cutting needle surrounded by an irrigating sleeve. During the phacoemulsification procedure, the tip of the cutting needle and the end of the irrigation sleeve are inserted into the anterior segment of the eye through a small incision in the outer tissue of the eye. The surgeon brings the tip of the cutting needle into contact with the lens of the eye, so that the vibrating tip fragments the lens. The resulting fragments are aspirated out of the eye through the cutting needle, along with irrigation solution provided to the eye during the procedure.
Challenges arise when pumps are integrated into the surgical hand piece to aspirate the lens fragments and irrigation solution away from the eye. For example, friction exists when one or more moving/rotating elements of the pump contact silicone tubing within the surgical hand piece. The silicon and/or other elastomeric tubing utilized in pumps is sufficiently tacky such that the tubing places a heavy torque load on a motor that is operating the pump. Thus, the motor can overheat or fail during use. One potential solution is to utilize a motor that can handle a heavier torque load. This, however, leads to a larger and heavier surgical hand piece, which can be difficult for a surgeon to operate, increases the chances of damage to the elastomeric tubing, and increases cost of the device. Other potential solutions such as exterior lubricating coating and/or self-lubricating silicon have been found to be ineffective and problematic because the lubricating material is stripped off of the tubing after a short period. Moreover, such solutions are generally implemented at the manufacturing stage, which increases the expense and reduces flexibility that an operator has prior to a surgical procedure.